What was found
AFT RT INBD LAVATORY REPORTED BY FLIGHT ATTENDANT HAVING ACRID SMELL, DISSIPATED BUT STILL HAD SLIGHT SMELL. CHECK REQUIRED MM05-51-56-201. SMELL PRESENT WHEN LIGHTS ON WITH DOOR LOCKED, SMELL DISSIPATED WHEN DOOR UNLOCKED & LIGHT OFF. R & R VERY WARM BALLAST & BALLAST IN CONNECTING LAVATORY. ACFT LEFT FOR PRECAUTIONARY REASONS AFTER ONE HOUR COULD NOT SMELL ANYTHING ALARMING IN NATURE LAVATORY OK FOR SERVICE.